In many situations, there is concern for differences between the HLA type of a cell source and the cell recipient. In situations where allogeneic cells or tissue are taken from a donor and introduced into a recipient, it is desirable that the donor and recipient be as closely HLA matched as possible The presence in the patient serum of antibodies against HLA antigens of the donor (donor specific crossmatch) or against a high percentage of HLA alleles (PRA testing) predicts a high risk of graft rejection.
The standard technique is microcytotoxicity, where patient serum is incubated with donor or panel lymphocytes, then with complement; the level of cytotoxicity is then estimated by discriminating between dead and viable cells using a dye. This method has numerous disadvantages: it is labor intensive; time consuming; requires isolation of cells; requires viable cells; is nonspecific; and requires a subjective evaluation. In addition, the methodology does not discriminate between IgG and IgM, where it is believed that IgM does not have a negative prognosis value as compared with IgG. Flow cytometry may also be used but requires cells and expensive instrumentation.
It is therefore of interest to provide alternative techniques which can be performed simply, can be automated, do not share the shortcomings described above, and provide a readily discernible result which is significant for the prognosis of graft acceptance.